It is known in the subterranean well drilling art that in some gas wells, liquid hydrocarbons (condensate) can form and accumulate in the vicinity of the well. In such reservoirs (sometimes referred to as retrograde condensate reservoirs), the presence of condensate can cause a large decrease in both the gas and condensate relative permeabilities, and thus the productivity of the well decreases. In some instances, the liquid blocking the flow of gas may be both condensate and water. The water may be from the subterranean formation or from operations conducted on the well.
One solution known in the art to address the formation of the condensate is to perform a formation fracturing and propping operation (e.g., prior to, or simultaneously with, a gravel packing operation) to increase the permeability of the production zone adjacent to the wellbore. For example, a fracture fluid such as water, oil, oil/water emulsion, gelled water or gelled oil is pumped down the work string with sufficient volume and pressure to open one or more fractures in the production zone of the formation. Optionally, the fracture fluid may carry a proppant, into the fractures to hold the fractures open following the fracturing operation. Proppants provide an efficient conduit for production of fluid from the reservoir to the wellbore, and may be naturally occurring sand grains, man-made or specially engineered (e.g., resin-coated sand), or high-strength ceramic materials (e.g., sintered bauxite).
The fracture fluid is forced into the formation at a flow rate great enough to fracture the formation allowing the entrained proppant to enter the fractures and prop the formation structures apart, producing channels that create highly conductive paths reaching out into the production zone, and thereby increasing the reservoir permeability in the fracture region. Although not wanting to be bound by theory, it is believed that the effectiveness of the fracture operation is dependent upon the ability to inject large volumes of hydraulic fracture fluid along the entire length of the formation at a high pressure and at a high flow rate.
Injection of methanol into condensate-blocked wells has been used to remove both water and condensate, and restore gas productivity for a period of time that may last up to several months. Again, not wanting to be bound by theory, it is believed that methanol provides an enhanced flow period by delaying the condensate bank formation and in some instances by removing the water from the near well region.
Despite advances in addressing the formation of the condensate, there is a continuing desire for alternative and/or improved techniques for addressing the condensate and/or water blocking issue.